Friday, December 08, 2006

Group competition, relatedness, and the evolution of human altruism

Science and Nature both seem to love research on human altruism/cooperation. Here is the latest by Sam Bowles from the Santa Fe Institute. The argument that he makes and the empirical and modeling evidence that he uses implies that human cooperation can be partly attributed to genetic relatedness between groups and conflict with other groups..so a sort of group/kin selection, the two of which are basically the same. There's a commentary by Rob Boyd and a related paper by Marin Nowak on the five rules for the evolution of cooperation (see below). Sam Bowles uses some relatedness data from modern hunter gatherers where the average degree of relatedness between group members turn out to be almost as high as cousins. I haven't looked too closely yet at how all this was measured, but sounds compelling.

Abstract: Humans behave altruistically in natural settings and experiments. A possible explanation—that groups with more altruists survive when groups compete—has long been judged untenable on empirical grounds for most species. But there have been no empirical tests of this explanation for humans. My empirical estimates show that genetic differences between early human groups are likely to have been great enough so that lethal intergroup competition could account for the evolution of altruism. Crucial to this process were distinctive human practices such as sharing food beyond the immediate family, monogamy, and other forms of reproductive leveling. These culturally transmitted practices presuppose advanced cognitive and linguistic capacities, possibly accounting for the distinctive forms of altruism found in our species.

Abstract: Cooperation is needed for evolution to construct new levels of organization. Genomes, cells, multicellular organisms, social insects, and human society are all based on cooperation. Cooperation means that selfish replicators forgo some of their reproductive potential to help one another. But natural selection implies competition and therefore opposes cooperation unless a specific mechanism is at work. Here I discuss five mechanisms for the evolution of cooperation: kin selection, direct reciprocity, indirect reciprocity, network reciprocity, and group selection. For each mechanism, a simple rule is derived that specifies whether natural selection can lead to cooperation.